Efficient unidirectional SPP launcher: coupling the SPP to a smooth surface for propagation.

Area of Science:

• Plasmonics
• Nanophotonics
• Optoelectronics

Background:

• Surface plasmon polaritons (SPPs) are electromagnetic waves confined to metal-dielectric interfaces.
• Efficiently launching SPPs from free-space light is critical for various nanophotonic applications.
• Existing methods often suffer from low coupling efficiency and significant propagation loss.

Purpose of the Study:

• To propose and numerically analyze a unidirectional surface plasmon polariton launcher.
• To achieve high coupling efficiency and long propagation length for SPPs.
• To investigate the impact of a dielectric spacer layer on SPP launching performance.

Main Methods:

• Numerical simulations were employed to model the proposed structure.
• The structure comprises a metallic slanted grating, a SiO2 dielectric layer, and a metal film on a quartz substrate.
• The interaction between the metal grating and film through the SiO2 layer was analyzed.

Main Results:

• The proposed structure demonstrates high coupling efficiency and long SPP propagation length.
• Inserting the SiO2 layer significantly enhances the conversion of incident light into SPPs.
• A smooth metal film-substrate interface reduces SPP dissipation, extending propagation distance by approximately 158% compared to a rough interface.
• Light conversion efficiency to SPPs improved by over 22.6% with the smooth interface.

Conclusions:

• The developed unidirectional SPP launcher offers superior performance compared to conventional structures.
• The SiO2 spacer layer and smooth interface are key to achieving high efficiency and long propagation distances.
• This work provides a promising platform for advancing integrated plasmonic devices and applications.